1. Field of the Invention
The present invention relates to an insufflation apparatus intended to enlarge an intended part in a cavity of the human body, while insufflating gas into the body cavity, to obtain a field of vision, through the endoscope, necessary to add a therapeutical and surgical treatment to that part in the body cavity.
2. Description of the Related Art
When the therapeutical and surgical treatment is to be added to the intended part in the body cavity, while viewing that part through the endoscope, for example, gas such as CO.sub.2 gas is insufflated into the body cavity to enlarge that part in the body cavity which is to be treated. A field of vision necessary to add the surgical treatment to the intended part in the body cavity is thus obtained so that it can be grasped enough how the surgical treatment advances in the body cavity.
In order to insufflate gas into the body cavity, the insufflation apparatus is used. It serves in this case to keep the pressure in the body cavity at a value set while controlling the pressure of gas supplied from a gas supply source such as the gas bomb by means of valves and decompression means.
Some of these insufflation apparatuses are disclosed in German Patent Publication No. 3000218 and German Patent Pre-opened Disclosure No. 3611018.
In the case of the former, one or more of plural gas insufflating pipes having the same flow rate is or are selected to adjust the flow rate of gas insufflated, and the amount of gas insufflated and the pressure in the body cavity are alternately measured. In the case of the latter, a decompression means is provided to adjust the operating pressure in a single gas insufflating pipe through an electric control circuit and the decompressing operation of this decompression means is changed to control the amount of gas insufflated into the body cavity without using any electromagnetic valve.
In the case of these insufflation apparatuses disclosed in the German Patent Publication and Application, however, the pressure of gas insufflated is low or about 50 mmHg. Therefore, the maximum flow rate obtained is only about 6 lits/min and this makes it difficult to insufflate gas into the body cavity at high speed.
Further, when the pressure of gas insufflated is made higher than 100 mmHg, for example, in the abovementioned insufflation apparatuses, the pressure in the body cavity is likely to exceed the value of pressure set, particularly in a case where the value of pressure set is small.